I've built two Mk3s: one for powerplant (output energy flow) and one for smeltery (input energy flow). But both of them are shown as energy producers and as energy consumers in the power production stats...

Screenshot: http://imgur.com/a/Ah43Z

My guess is that that doesn't have anything to do with the mod itself and more with the way that Factorio handles the power statistics. i.e. when one building produces, it simply counts all entities of that building and displays the number as such. That's why you get 2 even so only 1 is producing.

Same happens with accumulators. Even if you have some accumulators that run out of energy before others, the number still wouldn't change in the statistics place even so they don't provide any energy anymore because the game doesn't care about that.